A variety of antibacterial pyridonecarboxylic acid derivatives are known. For example, Japanese Patent Laid-Open No. 239857/'94 (corresponding to European Patent Application Laid-Open No. EP-A-603887) discloses compounds of the general formula (A) ##STR2## wherein: X.sub.1 and X.sub.2 are each a halogen atom;
R.sub.1 is an amino group which may have one or more substituents, or the like; PA1 R.sub.3 and R.sub.4 are each a hydrogen atom, an alkyl group or the like; PA1 Y is O, N, a methylene group or the like; PA1 Z is O, S, a methylene group or the like; PA1 m and n are each an integer of 0 to 2, the sum of them being 2 or 3; PA1 p, q and r are each an integer of 0 to 3, the sum of them being 0 to 3; PA1 A is N or C-X (in which X is a hydrogen atom, a halogen or the like); and PA1 R is a hydrogen atom or the like. PA1 X.sub.2 is hydrogen, amino or the like; PA1 R.sub.1 is alkyl, cycloalkyl or the like; PA1 R.sub.2 is hydrogen or the like; PA1 A is N or C-R.sub.5 in which R.sub.5 is hydrogen, halogen or the like; and PA1 Z is a group of the formula ##STR5## in which R.sub.3 and R.sub.4 are each hydrogen, methyl or the like. However, the bicyclic amino group (Z) constituting the substituent group at the 7-position in these compounds differs from that present in the compounds of the present invention, as to the mode of fusion between the first ring containing a nitrogen atom and the second ring containing an oxygen atom. PA1 X represents a hydrogen atom, a halogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group or an amino group which may be protected; PA1 Y represents a hydrogen atom or a halogen atom; PA1 A represents a nitrogen atom or a group of the formula C-Z in which Z represents a hydrogen atom, a halogen atom or a cyano group, represents a lower alkoxy group, a lower alkyl group, a lower alkylthio group, a lower alkenyl group or a lower alkynyl group (all of which may optionally be substituted by one or more halogen atoms), or combines with R to form a bridge represented by the formula --O--CH.sub.2 --CH(CH.sub.3)--; PA1 R.sub.1 and R.sub.2 may be the same or different and each represent a hydrogen atom, a lower alkyl group or an amino-protecting group; PA1 R.sub.3 represents a hydrogen atom or a lower alkyl group; PA1 R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8 and R.sub.9 may be the same or different and each represent a hydrogen atom, a halogen atom or a lower alkyl group; PA1 m is 0 or 1; and PA1 n and p may be the same or different and are each 0 or 1. PA1 (i) The compounds wherein R is a lower cycloalkyl group that may optionally be substituted by halogen, such as cyclopropyl or 2-fluorocyclopropyl, or a phenyl group that is substituted by one or more halogen atoms and/or an amino group, such as 2,4-difluorophenyl or 3-amino-4,6-difluorophenyl. PA1 (ii) The compounds wherein X is a hydrogen atom, a lower alkyl group such as methyl, or an amino group. PA1 (iii) The compounds wherein Y is a fluorine atom. PA1 (iv) The compounds wherein A is a nitrogen atom or C-Z in which Z is a hydrogen atom; a halogen atom such as a fluorine or chlorine atom; a cyano group; a lower alkoxy group that may optionally be substituted by halogen, such as methoxy or difluoromethoxy; a lower alkyl group such as methyl; a lower alkylthio group such as methylthio; a lower alkenyl group such as vinyl; or a lower alkynyl group such as ethynyl. PA1 (v) The compounds wherein R.sub.1 and R.sub.2 may be the same or different and are each a hydrogen atom or a lower alkyl group such as methyl. PA1 (vi) The compounds wherein R.sub.3 is a hydrogen atom. PA1 (vii) The compounds wherein R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8 and R.sub.9 may be the same or different and are each a hydrogen atom or a lower alkyl group such as methyl. PA1 R.sub.10 has the same meaning as described previously; PA1 R.sub.11 represents an alcohol-protecting group such as tert-butyidimethylsilyl, acetyl or tetrahydroyranyl; PA1 R.sub.12 represents a (lower alkyl)sulfonyl, a (halogeno lower alkyl)sulfonyl group or an arylsulfonyl group; PA1 R.sub.13 represents a hydrogen atom or a lower alkyl group; PA1 R.sub.1 ' represents an amino-protecting group; PA1 R.sub.2 ' and R.sub.3 ' each represent a lower alkyl group; PA1 X.sub.1, X.sub.2 and X.sub.3 each represent a halogen atom; PA1 q represents an integer of 1 to 3; and PA1 r is 0 or 1.
In these compounds of the general formula (A), the bicyclic amino group constituting the substituent group at the 7-position is composed of a first ring containing a nitrogen atom and a second ring containing an oxygen atom or the like. However, as to the substituent group on the first ring, these compounds differ from the compounds of the present invention which are represented by the formula (I) that will be given later. Moreover, in the compounds of the above formula (A) which are specifically described in the aforementioned Japanese Patent Laid-Open No. 239857/'94, only the following three groups are disclosed as examples of the bicyclic amino groups at the 7-position. ##STR3##
Moreover, Japanese Patent Laid-Open No. 192262/'94 (corresponding to European Patent Application Laid-Open No. EP-A-589318) discloses compounds of the general formula (B) ##STR4## wherein: X.sub.1 is halogen or nitro;